The invention relates to a device including a heating sample carrier, which comprises a carrying surface, an electrical heating system and a frame; and more particularly to such a device which includes a frame support adapted to receive the frame of the sample carrier.
The invention is used in the semiconductor industry to the extent to which, in order to manufacture circuits comprising layers on wafers, it is necessary to subject these layers to annealing treatments during the processing of the circuit, i.e. in situ.
The invention is used particularly in the manufacture of circuits of thin layers of a superconducting material, which manufacture necessitates annealing treatments.
In general, the invention is used in any construction necessitating the heating of a substrate in a closed space and especially in a vacuum or in an aggressive atmosphere.
A device commercially available intended to heat samples in a vacuum chamber is marketed by the French Company "MECA 2000", 37 Rue Saint Le'ger, 78 540 Vernouillet, France. The commercially available device is a 2" heating sample carrier. This known device consists of a standard sample carrier provided with a heating system. The sample carrier is solid. It has the general form of a large nail having a flat head in the form of a disk, the upper surface of this disk constituting the carrying surface of the sample. The heating system consists of a metallic filament arranged in the shape of a meander on the back surface of the disk. It raises the temperature of the sample arranged on the other surface by heating the metal of which the disk is composed. For this purpose, this metal must have a good thermal conductivity.
It is also important to note that the sample carrier is fixed to the framework of the vacuum chamber and cannot be removed in a simple manner. The heating filament is fed electrically by means of a transfer rod. Thus, the sample carrier is connected to the framework by the electrical supply wires of the heating filament. This electrical connection means prevents detaching the sample carrier from the framework, except during a complete disassembly operation, and even then cannot be detached by a simple displacement. However, there is a small latitude of displacement of the sample carrier parallel to the rod, but this results in only a small inclination of the sample with respect to the horizontal line.
The main disadvantage of this sample carrier is therefore that it is permanently fixed to a given vacuum chamber. It is therefore difficult to displace it in the chamber in which it is contained or from one chamber to the other.
For the envisaged use in annealing layers during the processing of integrated circuits or in the manufacture of layers at high temperatures, the known device moreover has a certain number of disadvantages.
In the first place, it is not apt to heat homgeneously samples of large surface area or several juxtaposed samples on the carrying surface leading to a large surface area to be heated. This is due to the mode of application and to the shape of the heating filament, which produces in the sample or samples arranged at the surface of the carrier considerable temperature gradients. In particular during operation, the temperature of the carrying surface is considerably higher at its center than at its periphery.
In the second place, the "image" of the meandering filament appears on the layer which has been subjected to the heat treatment.
In the third place, this device is very fragile. In fact, during the shaping of the meander constituting the filament, constrictions are formed in the metal, which makes the filament liable to break upon heating. This device therefore becomes inoperative after a very short operating time. As it has been found that this device is very complicated, its use therefore is very expensive.
In the fourth place, this sample carrier has a tendency to degased. This degas is caused by the material used to form the filament. Therefore, the user of this device cannot obtain a vacuum higher than 10.sup.-6 in the chamber torn. This limitation is unacceptable for the processing of layers in the integrated circuit technologies, in which most frequently values of 10.sup.-8 torr must absolutely be attained.
In the fifth place, this device can also be subject to damage during certain types of use. It is in fact not rare that in the integrated circuit technologies it is necessary to form metallic or insulating deposits in the vacuum space by a so-called sputtering method using gases, such as;
Ar, O, N, or H in combination with gases such as Cl.sub.2 or F, at a low partial pressure, to form a plasma. The use of the known device is excluded in this kind of application because the plasmas formed are corrosive for the heating filament and destroy it. PA1 the lower surface of the frame carries conductor tracks insulated from each other and from the frame to form the electrical supply system of the assembly of resistors, PA1 the upper surface of the frame support comprises a number of electrical supply pads, at least equal in number to the number of conductor tracks, arranged so that each pad can contact one of the conductor tracks on the frame, and PA1 the elements of the heating sample carrier, and especially the frame and the frame support, are not integral with each other but instead these elements fit together.